Proportional selector valve for selecting between two pressure sources

ABSTRACT

A selector valve selects between the supply of a primary pressure supply and a secondary pressure supply to a downstream use. The selector valve moves between a first position at which it supplies fluid from a primary line to the use, and a second position at which it supplies fluid only from a secondary line to the use. The selector valves moves through an intermediate position at which fluid is supplied from both supplies to the use.

BACKGROUND OF THE INVENTION

This application relates to a selector valve for selecting between twopressure sources to be delivered to a downstream use, wherein theselector valve has positions at which it delivers solely from each ofthe two sources, but has an intermediate position at which it mixes thetwo sources to be delivered to the use.

Selector valves are known, and are typically utilized to supply a fluidfrom alternate sources to a downstream use. In one proposed application,two distinct oil pumps deliver oil to the selector valve. The selectorvalve selects between the two oil supplies, and delivers the oil to adownstream use. In one application this downstream use is a gear box fora geared architecture gas turbine engine.

The purpose of this selector valve is to ensure that adequate oil issupplied. Thus, there is a primary oil pump that will typically bedelivered through the selector valve to the gear box. However, if thepressure of this primary oil pump drops below a predetermined level, theselector valve will move toward another position at which it willdeliver oil from a secondary oil pump.

Selector valves such as mentioned above typically toggle or snap betweenthe two extreme positions. Thus, they tend to oscillate between the twopositions, creating unwanted noise, and a non-smooth operation.

SUMMARY OF THE INVENTION

In the disclosed embodiment of this invention, a selector valve selectsbetween two distinct pressure sources to be delivered to a downstreamuse. As the selector valve moves from one of two positions to the other,it moves through an intermediate position at which it delivers fluidfrom both sources to the use.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system incorporating a selector valve.

FIG. 2 shows a selector valve in a first position.

FIG. 3 shows a selector valve in an intermediate position.

FIG. 4 shows a selector valve in yet another position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An oil supply system for a gear box 20 for a geared architecture gasturbine engine is illustrated in FIG. 1. Oil is supplied through a line21 to the gear box 20. A selector valve 22 alternatively selects oilfrom a primary oil pump 24 and a secondary oil pump 26. Primary oil pump24 delivers oil through the line 25 to the selector valve, and secondaryoil pump 26 delivers oil to the selector valve through a line 27.

As shown in FIG. 2, the selector valve 22 is in its normal operationalposition. Oil passes from the line 25 into a chamber 36, into a supplywindow 38, and then to the supply line 21. As can be also appreciated, atap 32 takes oil from the supply line 25 into a chamber 34 on one sideof a piston 30. The piston 30 further has a sealing land 39, and anopposed land 48. The piston has a land 31 facing chamber 34.

The secondary supply line 27 communicates oil into a chamber 50. Withthe piston in the position shown in FIG. 2, oil in the chamber 50 isdelivered directly into a bypass line 52. Also, oil from the secondarysupply line 27 passes through a tap 40 into a chamber 44. Also inchamber 44 is a spring 42, and a stop 46.

As long as the pressure of the oil from the main supply line 25 issufficient to overcome the force from the secondary oil in chamber 44,and the spring 42, the piston 30 remains in the position illustrated inFIG. 2. The sealing land 39 blocks communication of oil from thesecondary supply line 27 to the window 38. Oil from the primary oil pumpis delivered to the line 21.

However, if the pressure begins to drop, the piston moves through theposition shown in FIG. 3. As it does move to this position, the sealingland 39 no longer seals chamber 50 from window 38. At the same time,since the sealing land 39 extends for an axial distance that is lessthan the size of the window 38, the chamber 36 also communicates withthe window 38. In this position, there is a proportional mixture of oilfrom the two supply lines 25 and 27 being delivered to the line 21heading to the downstream use.

If the pressure of the primary oil supply at line 25 continues to drop,the piston 30 continues to moves to the right until it reaches theposition shown in FIG. 4. At this point the sealing land 39 blockscommunication of the chamber 36 to the window 38. Also, the land 48 hasblocked the secondary bypass 52. Oil from the secondary oil pump is nowdelivered to the line 21.

This selector valve will not snap or toggle between the two extremepositions, but instead will move smoothly through the mixture positionsuch as shown in FIG. 3. While this application discusses andillustrates three “positions,” of course, in real life, the piston movesthrough an infinite number of positions within the valve housing. Thepositions as illustrated and claimed in this application merelyillustrate that there are intermediate locations at which the valve willproportionally mix the fluid from the two sources.

While this application does describe the valve utilized in an oil supplysystem for a gear box, many other applications would be apparent for theinventive valve. Also, the valve can be utilized to proportionally mixand select between sources of fluids other than oil.

Although embodiments have been disclosed, a worker of ordinary skill inthis art would recognize that certain modifications would come withinthe scope of this invention. For that reason, the following claimsshould be studied to determine the true scope and content of thisinvention.

1. A selector valve for selecting between two pressure sources to bedelivered to a downstream use comprising: a valve housing; a pistonmovable within a bore in said valve housing; a first supply line forcommunicating a primary supply into a first chamber; a second supplyline to communicate a secondary supply into a second chamber, and awindow to communicate to a line leading to a downstream use for thesupply; and said piston being operable to move between a first positionat which it connects said first chamber to said window, and blockscommunication between said second chamber to said window, a secondposition at which it connects said second chamber to said window andblocks communication between said first chamber to said window, and athird position which is intermediate said first and second positions,and which connects both of said first and second chambers to saidwindow, said valve moving through said third position as it movesbetween said first and second positions.
 2. The valve as set forth inclaim 1, wherein said piston includes a first land for seeing thepressure from said primary supply, a second land for seeing the pressurefrom said secondary supply, and a sealing land for selectively blockingcommunication between said first and second chamber and said window. 3.The valve as set forth in claim 2, wherein said sealing land extends foran axial distance that is less than an axial distance of said windowsuch that said window can communicate with both said first and secondchambers while said piston is in said third position.
 4. The valve asset forth in claim 2, wherein said second land sees a pressure fromsecondary supply and a spring force.
 5. The valve as set forth in claim2, wherein a tap extends from said primary supply to a side of saidfirst land which is remote from said first chamber.
 6. The valve as setforth in claim 5, wherein a tap from said secondary supply extends to anopposed side of said second land from said second chamber.
 7. The valveas set forth in claim 1, wherein the fluid from the two supply lines isproportionally mixed in the third position.
 8. The valve as set forth inclaim 1, wherein the two pressure sources are oil pumps.
 9. An oilsupply system for a gear box of a gas turbine engine comprising: a firstpump for delivering oil into a first supply line; a second pump fordelivering oil into a second supply line; an outlet line for deliveringoil to a gear box; and a selector valve positioned between said firstand second supply lines and said outlet line, said selector valve havinga valve housing, a piston movable within a bore in said valve housing, afirst supply line for communicating a primary oil supply into a firstchamber, a secondary supply line to communicate a secondary oil supplyinto a second chamber, and a window to communicate to a line leading toa downstream use for the oil, and said piston being operable to movebetween a first position at which it supplies oil from said firstchamber to said window, and block oil from moving from said secondchamber to said window, a second position at which it allows oil to movefrom said second chamber to said window and blocks oil from moving fromsaid first chamber to said window, and a third position which isintermediate said first and second position, and which allows oil tomove from both of said first and second chambers to said window, saidvalve moving through said third position as it moves between said firstand second position.
 10. The system as set forth in claim 9, whereinsaid piston includes a first land for seeing the pressure from saidprimary oil supply, a second land for seeing the pressure from saidsecondary oil supply, and a sealing land for selectively blockingcommunication between said first and second chamber and said window. 11.The system as set forth in claim 10, wherein said sealing land extendsfor an axial distance that is less than an axial distance of said windowsuch that said window can communicate with both said first and secondchambers while said piston is in said third position.
 12. The system asset forth in claim 10, wherein said second land sees a pressure fromsecondary oil supply and a spring force.
 13. The system as set forth inclaim 10, wherein a tap extends from said primary oil supply to a sideof said first land which is remote from said first chamber.
 14. Thesystem as set forth in claim 13, wherein a tap from said secondary oilsupply extends to an opposed side of said second land from said secondchamber.
 15. The system as set forth in claim 9, wherein the valveproportionally mixes the oil from the two supply lines when in the thirdposition.
 16. The system as set forth in claim 9, wherein the gear boxis associated with a gas turbine engine.